The present invention relates to glasses for ophthalmic applications which, in addition to the properties of ultraviolet radiation (UV) absorption and high transmission in the visible (absence of coloration), have a low density, as well as corrective lenses produced from these glasses.
These glasses are characterized by an index of refraction (n.sub.d) of 1.523.+-.0.004, an Abbe number (V.sub.d) between 51-59, and a density (D) less than 2.43 g/cm.sup.3. Their transmission at 400 nm is, for a thickness of 2 mm, greater than 89%. Their UV cutoff, defined as the wavelength for which the transmission is equal to 1% for a thickness of 2 mm, is between 310-335 nm. Moreover, they exhibit excellent chemical durability (A.O. test).
Lenses of inorganic glass ("white" or tinted) for ophthalmic use have, to a very great extent, an index of refraction n.sub.d =1.523. The "white" (or tinted) glasses used at the present time and which exhibit in certan cases a UV cutoff higher than 300 nm, have a density at least equal to 2.54 g/cm.sup.3. A reduction of the density and, consequently, of the weight of the lens, offers an obvious advantage for the wearer and that regardless of the power of the lens. The lightening of the lens by the glasses of this invention is about 6.5-7%.